feat: override color interpretation based on GDAL metadata

src/async_geotiff/_colorinterp.py

@@ -6,7 +6,7 @@
 
 from async_tiff.enums import ExtraSamples
 
-from .enums import ColorInterp, PhotometricInterpretation
+from async_geotiff.enums import ColorInterp, PhotometricInterpretation
 
 if TYPE_CHECKING:
     from collections.abc import Sequence
@@ -23,7 +23,7 @@ def infer_color_interpretation(  # noqa: PLR0911
         case None:
             return (ColorInterp.UNDEFINED,) * count
         case PhotometricInterpretation.BLACK_IS_ZERO:
-            return (ColorInterp.GRAY,) * count
+            return (ColorInterp.GRAY,) + (ColorInterp.UNDEFINED,) * (count - 1)
         case PhotometricInterpretation.RGB:
             if count <= 2:
                 raise NotImplementedError(

src/async_geotiff/_gdal_metadata.py

@@ -1,10 +1,12 @@
 from __future__ import annotations
 
 from collections import defaultdict
-from dataclasses import dataclass
+from dataclasses import dataclass, field
 
 import defusedxml.ElementTree as ET  # noqa: N817
 
+from async_geotiff.enums import ColorInterp
+
 
 @dataclass
 class BandStatistics:
@@ -36,6 +38,18 @@ class GDALMetadata:
 
     scales: tuple[float, ...]
 
+    colorinterp: dict[int, ColorInterp] = field(default_factory=dict)
+    """A mapping of 1-based band index to overridden ColorInterp.
+
+    When present, these values override what would otherwise be inferred
+    from the photometric interpretation tag.
+    """
+
+
+LOWER_CASE_COLORINTERP_MAPPING: dict[str, ColorInterp] = {}
+for color in ColorInterp:
+    LOWER_CASE_COLORINTERP_MAPPING[color.name.lower()] = color
+
 
 def parse_gdal_metadata(  # noqa: C901
     gdal_metadata: str | None,
@@ -53,37 +67,37 @@ def parse_gdal_metadata(  # noqa: C901
     band_statistics: defaultdict[int, BandStatistics] = defaultdict(BandStatistics)
     offsets: list[float] = [0.0] * count
     scales: list[float] = [1.0] * count
+    colorinterp: dict[int, ColorInterp] = {}
 
     for elem in root.findall("Item"):
         name = elem.attrib.get("name")
         sample = elem.attrib.get("sample")
+        role = elem.attrib.get("role")
         text = elem.text or ""
         match name:
             # Add 1 to get a 1-based band index to match GDAL.
-            case "STATISTICS_MAXIMUM":
-                assert sample is not None  # noqa: S101
+            case "STATISTICS_MAXIMUM" if sample is not None:
                 band_statistics[int(sample) + 1].max = float(text)
-            case "STATISTICS_MEAN":
-                assert sample is not None  # noqa: S101
+            case "STATISTICS_MEAN" if sample is not None:
                 band_statistics[int(sample) + 1].mean = float(text)
-            case "STATISTICS_MINIMUM":
-                assert sample is not None  # noqa: S101
+            case "STATISTICS_MINIMUM" if sample is not None:
                 band_statistics[int(sample) + 1].min = float(text)
-            case "STATISTICS_STDDEV":
-                assert sample is not None  # noqa: S101
+            case "STATISTICS_STDDEV" if sample is not None:
                 band_statistics[int(sample) + 1].std = float(text)
-            case "STATISTICS_VALID_PERCENT":
-                assert sample is not None  # noqa: S101
+            case "STATISTICS_VALID_PERCENT" if sample is not None:
                 band_statistics[int(sample) + 1].valid_percent = float(text)
-            case "OFFSET":
-                assert sample is not None  # noqa: S101
+            case "OFFSET" if sample is not None:
                 offsets[int(sample)] = float(text)
-            case "SCALE":
-                assert sample is not None  # noqa: S101
+            case "SCALE" if sample is not None:
                 scales[int(sample)] = float(text)
+            case "COLORINTERP" if role == "colorinterp" and sample is not None:
+                colorinterp[int(sample) + 1] = LOWER_CASE_COLORINTERP_MAPPING[
+                    text.lower()
+                ]
 
     return GDALMetadata(
         band_statistics=dict(band_statistics),
         offsets=tuple(offsets),
         scales=tuple(scales),
+        colorinterp=colorinterp,
     )

src/async_geotiff/_geotiff.py

@@ -215,12 +215,20 @@ async def open(
     @property
     def colorinterp(self) -> tuple[ColorInterp, ...]:
         """The color interpretation of each band in index order."""
-        return infer_color_interpretation(
-            count=self.count,
-            photometric=self.photometric,
-            extra_samples=self._primary_ifd.extra_samples or [],
+        interps = list(
+            infer_color_interpretation(
+                count=self.count,
+                photometric=self.photometric,
+                extra_samples=self._primary_ifd.extra_samples or [],
+            ),
         )
 
+        if gdal_metadata := self._gdal_metadata:
+            for band_index, color_interp in gdal_metadata.colorinterp.items():
+                interps[band_index - 1] = color_interp
+
+        return tuple(interps)
+
     @property
     def colormap(self) -> Colormap | None:
         """Return the Colormap stored in the file, if any.

tests/image_list.py

@@ -10,9 +10,14 @@
     ("rasterio", "float32_1band_lerc_zstd_block32"),
     ("rasterio", "uint16_1band_lzw_block128_predictor2"),
     ("rasterio", "uint16_1band_scale_offset"),
+    ("rasterio", "uint8_1band_and_alpha_deflate_block64_cog"),
+    ("rasterio", "uint8_1band_deflate_block128_unaligned_mask"),
+    ("rasterio", "uint8_1band_deflate_block128_unaligned_predictor2"),
     ("rasterio", "uint8_1band_deflate_block128_unaligned"),
     ("rasterio", "uint8_1band_lzma_block64"),
     ("rasterio", "uint8_1band_lzw_block64_predictor2"),
+    ("rasterio", "uint8_1band_zstd_level1_block64"),
+    ("rasterio", "uint8_nonrgb_deflate_block64_cog"),
     ("rasterio", "uint8_rgb_deflate_block64_cog"),
     ("rasterio", "uint8_rgb_webp_block64_cog"),
     ("rasterio", "uint8_rgba_webp_block64_cog"),
@@ -35,6 +40,7 @@
 
 ALL_TEST_IMAGES: list[tuple[str, str]] = [
     *ALL_DATA_IMAGES,
+    ("rio-tiler", "cog_rgb_with_stats"),
     # YCbCr is auto-decompressed by rasterio
     ("vantor", "maxar_opendata_yellowstone_visual"),
     ("source-coop-alpha-earth", "xjejfvrbm1fbu1ecw-0000000000-0000008192"),

tests/test_colorinterp.py

@@ -6,7 +6,7 @@
 
 import pytest
 
-from .image_list import ALL_DATA_IMAGES
+from .image_list import ALL_TEST_IMAGES
 
 if TYPE_CHECKING:
     from .conftest import LoadGeoTIFF, LoadRasterio
@@ -15,14 +15,19 @@
 @pytest.mark.asyncio
 @pytest.mark.parametrize(
     ("variant", "file_name"),
-    ALL_DATA_IMAGES,
+    ALL_TEST_IMAGES,
 )
 async def test_colorinterp(
     load_geotiff: LoadGeoTIFF,
     load_rasterio: LoadRasterio,
     variant: str,
     file_name: str,
 ) -> None:
+    if (variant == "vantor" and file_name == "maxar_opendata_yellowstone_visual") or (
+        variant == "rio-tiler" and file_name == "cog_rgb_with_stats"
+    ):
+        pytest.skip("Should our colorinterp map YCbCr to RGB?")
+
     geotiff = await load_geotiff(file_name, variant=variant)
     colorinterp = geotiff.colorinterp
     assert colorinterp is not None, "Expected color interpretation to be present."